The present disclosure relates generally to systems and methods for performing resection of bone, and more particularly to systems and methods for preparing the proximal tibia to receive a tibial prosthetic implant component.
The knee joint comprises the interface between the distal end of the femur and the proximal end of the tibia. In a properly-functioning knee joint, medial and lateral condyles of the femur pivot smoothly along menisci attached to respective medial and lateral condyles of the tibia. When the knee joint is damaged, the natural bones and cartilage that form the joint may be unable to properly articulate, which can lead to joint pain and, in some cases, interfere with normal use of the joint
In some situations, surgery is required to restore normal use of the joint and reduce pain. Depending upon the severity of the damage, the surgery may involve partially or completely replacing the joint with prosthetic components. During such knee replacement procedures, a surgeon resects damaged portions of the bone and cartilage, while attempting to leave healthy tissue intact. The surgeon then fits the healthy tissue with artificial prosthetic components designed to replicate the resected tissue and restore proper knee joint operation.
One knee replacement procedure—total knee arthroplasty (“TKA”)—involves the resection of some or all of each of the medial and lateral condyles of both the femur and tibia and the removal of the fibro-cartilage menisci located at the femorotibial interface. A prosthetic femoral component, typically made of cobalt-chromium alloy or other strong, surgical-grade metal, is fitted and secured to the distal end of the femur to replace the resected portion of the femur. Similarly, a prosthetic tibial component, the base of which is also typically made of cobalt-chromium alloy, titanium, or other suitable metal, is fitted and secured to the proximal end of the tibia to replace the resected portion of the tibia.
In some situations, the patient's bone at the knee joint may have deteriorated to a point which requires TKA surgery, but one or more of the patient's cruciate ligaments (e.g., the anterior cruciate ligament (ACL) and/or posterior cruciate ligament (PCL)) are in sufficient condition to provide adequate joint stability. Maintaining the native cruciate ligaments is often advantageous, as doing so is generally thought to aid in proprioception (the ability to sense where parts of the body are in relation to each other) and could make activities like climbing stairs feel more stable or natural. Preserving the cruciate ligaments can also promote more normal front to back knee motion, which can enhance the patient's ability to maintain preoperative range of motion, particularly as it relates to deep flexion. The ligaments also aid in joint stability.
Each of the native cruciate ligaments connects to one of the femoral condyles, passes within the intercondylar region of the femur, and connects to the center-top portion of the tibia called the tibial eminence. In order to accommodate the passage of the cruciate ligaments, the femoral and tibial implant components used in cruciate-retaining procedures typically comprise intercondylar cutaways that define a vertical passage between the intercondylar fossa of the femur and the tibial eminence. The medial and lateral components of each of the femoral and tibial prosthetic components are separated by a deep intercondylar passage (or “notch”) that allows for passage of cruciate ligaments vertically through the notch.
During normal operation of the knee joint, the cruciate ligaments can exert significant tension at the attachment site of the tibia called the tibial eminence. In a healthy knee joint, there is sufficient tissue surrounding the tibial eminence to aid in the distribution of this force across the surface of the tibia. Installation of a cruciate-retaining tibial prosthetic component, while aimed at preserving an attachment site at the tibial eminence, typically requires significant removal of the surrounding native tissue of the tibia to make way for installation of the tibial implant. This surrounding tissue provides much of the attachment strength that counteracts the tension applied by the cruciate ligaments, and removal of this tissue can weaken the attachment strength of the tibial eminence.
Present methods of tibial preparation (i.e. removal of bone to receive the tibial implant) can result in inadvertent removal of even more tissue than is necessary for installation of the tibial implant, which further weakens the strength of the tibial eminence and can result in implant failure. In particular, present methods employ manual oscillating sagittal saws to make planar cuts. Manual saws making horizontal cuts can overcut into the eminence, and manual saws making vertical cuts can cut too deep into the tibial bone. These overcuts weaken the tibial eminence and the cruciate ligament attachment. Additionally, traditional planar saws can create sharp corners and high stress risers, which puts additional stress at the tibial eminence. Attempts to improve the undercut problem, particularly at the lateral overcuts, and reduce stress risers, have led to adding drilled pins placed at the intersection of the resected portion and the remaining tibial eminence portion to stop overcutting. However, saw blades often skive and can still result in overcutting and stress risers.